The present invention relates to well treating uses of phosphomethyl and amino-substituted macrocyclic polyethers, to processes for their preparation, and to complexes formed from them. The present invention further relates to compositions, especially aqueous compositions, containing such polyethers which can be used as cleaning agents, especially for cleaning a well penetrating an underground formation and optionally cleaning formation parts in the vicinity of the said well. Finally, the present invention also relates to cleaning processes using such macrocyclic polyethers.
Synthetic macrocyclic polyethers (often referred to as "crown ethers") are of great interest in that they contain intra-molecular cavities which are fit to accommodate alkali metal or alkaline earth metal ions depending on the particular shape of the polyether employed. Therefore, salts of alkaline earth metals which are substantially insoluble in water can be solubilized by aqueous solutions of such polyethers. It is also possible to dissolve such salts in organic solvents such as benzene or toluene in the presence of such polyethers. Referrence is made in this respect to British Patent Specification No. 1,304,367 and to Acc. of Chem. Res., Volume 11 (1978) pages 49-57.
Various well treating procedures for removing various types of scales with aminopolyacetic acid salt chelating agents, such as EDTA (ethylenediaminetetraacetic acid), are known. For example, U.S. Pat. No. 2,396,938 (filed in 1944) describes removing boiler scale with aqueous solutions of such a chelant and an alkali metal hydroxide. U.S. Pat. No. 2,802,788 (filed in 1952) describes a radiator cleaning composition in which such a chelant salt is included in an aqueous solution along with an inorganic chelant, e.g., sodium tripolyphosphate. U.S. Pat. No. 3,308,065 (filed in 1963) describes a substantially one-pore volume treatment for removing calcium sulfate-containing scale with an ammoniated or aminated chelant, e.g., an ammonium salt of EDTA. U.S. Pat. No. 3,660,287 (filed in 1967) describes a similar treatment for dissolving calcium sulfate-containing scale with a mixture of an EDTA salt and water soluble inorganic carbonate salt. While the above processes were consistent in utilizing an amount of solution which about filled one pore volume of the region within which the scale was to be removed and using a concentration of chelant such that that volume of the solution contained a stoichiometric excess relative to the amount of scale to be dissolved, U.S. Pat. Nos. 2,877,848 and 4,030,548 relate to using relatively dilute solutions. The U.S. Pat. No. 4,030,548 describes the tendancy for relatively concentrated EDTA solutions to become quickly saturated with a Ba-EDTA complex and suggests a one-through-dynamic wash treatment with enough solution to gradually remove the solid.
Numerous monocyclic and bicyclic macrocyclic polyethers and their tendancies to chelate with alkaline earth metals and to dissolve salts of such metals are disclosed in "Tetrahedron Letters" No. 34 (1969), pages 2889-2892. U.S. Pat. Nos. 3,888,877 and 3,966,766 relate to such polyethers and their general utility as chelating agents.
One co-pending patent application Ser. No. 951,701, filed Oct. 16, 1978 by F. DeJong, G. J. Torny-Schutte and D. N. Reinhoudt, now U.S. Pat. No. 4,215,000, relates to dissolving a barium sulfate solid from a remote location into which fluid can be flowed by contacting that solid with an aqueous solution consisting essentially of: water, a bicyclic macrocyclic polyether, a proportion of alkali metal salt of an organic acid which is less than that of the polyether but is sufficient to catalytically increase the rate of barium solid dissolving by the polyether, and enough dissolved alkaline inorganic alkali metal or ammonium compound to provide a solution pH of at least about 8.
Another co-pending patent application by the same inventors, Ser. No. 003,155, filed Jan. 15, 1979, now U.S. Pat. No. 4,190,462, relates to a process comprising contacting the surfaces to be cleaned with an aqueous solution consisting essentially of water, a monovalent cation salt of a monocyclic macrocyclic polyether containing at least two nitrogen-linked carboxymethyl groups and enough dissolved alkaline inorganic alkali metal or ammonium compound to provide a solution pH of at least about 8. That polyether contains an intra-molecular cavity or crypt which is selectively receptive to multivalent cations. And, the aqueous solution is both capable of relatively rapidly dissolving barium sulfate scale and free of any bicyclic macrocyclic polyether.